Scanning electron microscopy, transmission electron microscopy, and various transmission electron cytochemical and tracer techniques will be used to study aminonucleoside nephrosis. Special attention will be paid to determine what role the visceral epithelium, glomerular basement membrane and uriniferous tubules play in producing the proteinuria associated with the nephrotic syndrome. Attention will also be focused on determining what changes occur in and the possible physiological significance of the newly discovered (1) Bowman's capsule cilia and cilia found throughout the uriniferous tubules; (2) microprojections found on the glomerular visceral epithelium and endothelium and throughout the uriniferous tubules; (3) the proximal tubule brush borders and microcraters; (4) proximal tubule tendrils; and (5) podocyte microtubules. Finally, the cytochemical nature of intracytoplasmic granules and luminal casts which characterize the nephrotic syndrome will be studied.